phrase="Don't panic!"
plist = list(phrase)  # list() 可以将str to(转) list 字符串转列表
print(phrase)
print(plist)

on_str = ''.join(plist[1:3])
print(on_str)
new_phrase = on_str+''.join(plist[5]+plist[4]+plist[7]+plist[6])
print(plist)
print(new_phrase)